Cell Structure Flashcards
What are the features of eukaryotic cells?
- cytoplasm
- plasma membrane/ cell surface membrane
- membrane bound organelles
Define membrane bound organelles
Organelles which are covered by a membrane to keep them separate from the rest of the cell
State the membrane bound organelles present in a eukaryotic cell
- nucleus
- rough and smooth endoplasmic reticulum
- golgi apparatus
- mitochondria
- lysozymes
- cilia and undulipodia
- chloroplasts
- vacuole
What sub-cellular structures contain their own DNA?
- nucleus
- mitochondria
- chloroplasts
State the different parts that make up the nucleus
- nuclear envelope
- nucleolus
- chromatin
What is the function of the nuclear envelope?
- Separates the contents of the nucleus from the rest of the cell
- double membrane, contains pores
- at points wherein the inner and outer membranes fuse, dissolved substances can pass through
- pores enable larger substances (such as mRNA and hormones) to enter and leave the nucleus
What is the function of the nucleolus?
- ribosomes are made here
- no membrane around it
- contains RNA
What is the function of the chromatin?
Genetic material (DNA & histone proteins) condense to chromosomes during division
What is the difference between chromatin when the cell is dividing and when its not dividing?
- when cell is not dividing, chromatin is spread out or extended
- when cell is about to divide, chromatin condenses and coils tightly into chromosomes
State the components of the rough endoplasmic reticulum
- cisternae
- ribosomes
What are the cisternae?
Series of flattened sacs
What is the function of cisternae?
Form channels to transport substances
What is the function of the ribosomes?
- protein synthesis occurs and proteins pass through the cisternae to Golgi Apparatus OUT of the cell
- RER has a large surface area for ribosomes
What is the difference between the rough ER and the smooth ER?
Rough ER has ribosomes on its surface, whereas smooth ER does not
What is the function of the cisternae in the smooth ER?
- continuous with nuclear membrane to transport lipids
- contains enzymes that catalyse reactions involved in lipid metabolism and synthesis, and carbohydrate metabolism
Describe the Golgi Apparatus
Series of fluid filed flattened and curved sacs, with vesicles surrounding the edges
What are the components of the Golgi Apparatus?
- stack of membrane flattened sacs
- vesicles
- secretory vesicles
What is the function of the stack of membrane bound flattened sacs?
Proteins modified by adding sugar to make glycoproteins or lipids to make lipoproteins
What is the function of the vesicles?
contains proteins that fuse with the Golgi apparatus
What is the function of secretory vesicles?
Take modified proteins out of the golgi apparatus
What is the overall function of the golgi?
Processes and packages proteins and lipids
What is the difference between secretory vesicles and transport vesicles?
- secretory vesicles store and release materials into the cell or to the extracellular environment
- whereas transport vesicles move materials within the cell
What are the components that make up mitochondria?
- outer membrane
- inner membrane that folds into cristae
- inner part of mitochondrion is a fluid filled matrix
What is the function of mitochondria?
It is the site of ATP production during aerobic respiration
Why can mitchondria come in different shapes?
Depends on how the cell has been cut, for example if cut through the top middle the mitochondria may appear circular, but if cut through the side middle, the mitochondria may appear rod-shaped
What are the different shapes that mitochondria can come in?
- spherical
- rod-shaped
- branched
What are lysozymes?
- small bags formed in the golgi
- surrounded by a single membrane
What is the function of a lysozyme?
Contains powerful hydrolytic enzymes to digest and engulf substances/ organelles
What are cilia and undulipodia?
Protrusions from the cell and are surrounded by the cell membrane
What is the function of cilia?
To move or monitor substances
What is the function of undulipodia?
Enables sperm to move
What is the function of a singular cillium?
- acts as an antenna
- contains receptors that can detect movement + signals about the immediate environment
What are the components present in a chloroplast?
- thylakoids
- stroma
What is a thylakoid?
- Stacks of flattened membrane sacs, containing chlorophyll
- each stack is called a granum
What is the function of a thylakoid?
First stage of photosynthesis occurs here
What is the first stage of photosynthesis?
Light energy is trapped + used to make ATP
What is the stroma?
Fluid filled matrix
What is the function of a stroma?
Second stage of photosynthesis occurs here
What is the second stage of photosynthesis?
Hydrogen reduces carbon dioxide to make carbohydrates
What are the components of a vacuole?
- tonoplast
- cell sap
What is a tonoplast?
Single membrane, contains fluid
What are the functions of a tonoplast?
Filled with water and solutes + maintains cell stability (pushes against cell wall when full, making cell turgid)
What is the function of cell sap?
Makes cell stable
Describe the interrelationship between the organelles involved in the production and secretion of proteins
- Nucleus releases mRNA
- mRNA translated by the ribosome onto the rough ER
- Proteins pass into the cisternae of the RER
- Vesicles break off the cisternae
- Vesicle carries protein to golgi and fuses with it
- Proteins are modified by adding carbs/ lipids
- Secretory vesicles break away from Golgi and move to cell membrane
- SV fuses with cell membrane
- Proteins released by exocytosis
What are the non membrane bound organelles?
- ribosomes
- centrioles
- cellulose cell wall
What are the components of ribosomes?
Made of a large subunit and a small subunit
Where are ribosomes made?
Made in the nucleolus and combine in the cytoplasm
How large are eukaryotic ribosomes?
20nm in diameter
Where are ribosomes found?
- attached to the RER
- some stay in the cytoplasm
What is the function of the ribosome?
Assemble proteins
What is the difference between the ribosomes in the cytoplasm vs the RER?
- RER: synthesis proteins that will be exported out of the cell
- cytoplasm: site of assembly of proteins for within the cell
What are centrioles?
2 bundles of microtubules at right angles to each other
What are microtubules made of?
Tubulin
What is the function of a centriole?
- Spindle made from these during cell division + chromosomes attach to be pulled
- forms cilia and undulipodia
How do centrioles form cilia and undulipodia?
- microtubules line up at the edge of the cell
- and spout outwards from each centriole, forming a cilium or undulipodium
- this only occurs for specialised cells
What subcellular structures are exclusive to plant cells?
- large permanent vacuole
- chloroplasts
- cellulose cell wall
What subcellular structures are exclusive to animal cells?
Centrioles
Define cytoskeleton
A dynamic network of protein structures within the cytoplasm
What is the function of a cellulose cell wall?
- provide strength and support
- maintain cell shape
- contribute to the strength and support of the whole plant
- permeable
What are the components of the cytoskeleton?
- tubulin microtubules form a track (continuously changing) to move organelles using motor proteins
- microfilaments made from actin contribute to the stability and movement of the whole cell
- intermediate filaments anchor nucleus and stabilise tissues
What are the motor proteins present in the cytoplasm and what is their function?
- myosins, kinesins, dyneins
- move substances around the cytoskeleton
- they are also enzymes and have a site that binds to and enables hydrolysis of ATP as their energy source
What is the function of a cytoskeleton?
- cell support/ stability/ scaffolding/ maintaining the shape
- movement of cilia/ flagella/ undulipodia or use of flagellum/ undulipodium to move
- change shape of cell
- organelles moved
- movement of chromosomes/ mRNA/ vesicles
- formation of spindle
- mainly: providing mechanical strength to cells, aiding transport within cells and enabling cell movement
What are the similarities between prokaryotic and eukaryotic cells?
- contain cytoplasm
- plasma membrane
- non membrane bound organelles
- contain DNA & RNA
What are th differences between prokaryotic and eukaryotic cells?
- smaller (0.5 - 5 micrometers in diameter) than eukaryotic cells (10-100 micrometers in diameter)
- don’t contain membrane bound organelles
- cytoskeleton is much less developed
- cell wall made of peptidoglycan
- havesmaller ribosomes (70s compared to 80s)
- no nucleus: DNA floats in cytoplasm as a loop, not wound around histone proteins
What are the subcellular structures exclusive to prokaryotic cells?
- flagella
- plasmid
- pili
- protective slime capsule
What is the function of flagella?
Rotates to move the cell
What is the function of plasmids?
Small loop of DNA
What is the function of pili?
Allows adherence of cells
What is the function of protective slime/waxy capsule?
Protects cell from physical and chemical attacks
How do prokaryotic cells divide?
Through binary fission